New Studies Indicate GSK's Pre-Pandemic Influenza Vaccine Can
Protect Against Different Strains of H5N1

PHILADELPHIA, LONDON, and RIXENSART, Belgium, March 05, 2007
/PRNewswire/ -- GlaxoSmithKline announces clinical trial data from
two new studies, which show, for the first time, that GSK's
candidate pre-pandemic split antigen H5N1 vaccine, formulated with
GSK's proprietary adjuvant system, provides a substantial level of
cross-immunity against a 'drifted' (diverse) strain of H5N1. It is
hoped that the immune response elicited with this vaccine, could
help prepare or 'prime' the immune system to rapidly respond
against variants of the H5N1 strain and therefore protect the
vaccinated population in the event of an H5N1 human pandemic.

In the first study presented at the IX International Symposium
on Respiratory Viral Infections (ISRVI), data demonstrated GSK's
proprietary adjuvanted candidate pre-pandemic vaccine, containing
very low levels of the Vietnam H5N1 antigen (3.8 micrograms),
elicits a strong cross-immune neutralizing antibody response in
humans against the Indonesian strain of the virus. The neutralizing
antibody seroconversion factor at Day 42 was shown to be 25 times
greater when the vaccine contained the adjuvant system compared
with that observed in the control group immunized with a
non-adjuvanted vaccine (77.1% vs. < 3%).

GSK's proprietary adjuvant system also displays powerful
antigen-sparing properties as the strong neutralizing response in
this study was obtained with only two doses of 3.8 micrograms HA
antigen administered 3 weeks apart. This could mean, in effect,
that by adding GSK's proprietary adjuvant system, vaccine
manufacturing capacity could be increased more than tenfold. The
vaccine was shown to have an acceptable safety profile when
compared to the control group. As expected, reactogenicity
(injection site tenderness) was slightly higher in the vaccine
group due to the use of the adjuvant system.

In a second study presented at ISRVI, the data showed that GSK's
proprietary adjuvanted pre-pandemic vaccine could protect against
two diverse H5N1 flu strains, again at very low levels of antigen.
The in vivo data from the pre-clinical studies demonstrated that
GSK's adjuvanted vaccine, containing the Vietnam H5N1 strain, was
not only able to protect against challenge with the vaccine virus
strain, but also provides 96% (22/23) cross- protection against a
lethal challenge with the drifted Indonesia strain of H5N1, giving
an additional boost to hopes that pre-pandemic vaccination is a
viable strategy for inclusion in pandemic preparedness plans.

Jean Stephenne, President, GlaxoSmithKline Biologicals, the
vaccine division of GSK, commented, "I am extremely encouraged by
the new trial data that has been reported today on GSK's candidate
pre-pandemic influenza vaccine. The data confirm that our
pre-pandemic influenza vaccine has the ability to recognize and
kill an H5N1 strain that is different to the one contained in the
vaccine. This means that proactive administration of our pre-
pandemic vaccine before or just after the start of the pandemic
could help to substantially slow down the spread of disease."

Pandemic influenza poses a serious global public health threat
with substantial estimated morbidity and mortality. The exact
strain that may cause an influenza pandemic cannot be accurately
predicted. Many experts, however,

believe that the avian H5N1 strain, now endemic in many bird
species across the world, is the most likely candidate pandemic
strain.

"We believe this vaccine will provide governments with a new
option to help protect their populations against the threat of a
future human influenza pandemic," commented David Stout, President,
GSK Pharmaceuticals.

This pivotal observer-blind, randomized study was conducted in
400 adults (18 to 60 years) to evaluate the reactogenicity and the
immune response of GSK's pre-pandemic candidate vaccine
administered at four antigen concentrations (3.8 micrograms, 7.5
micrograms, 15 micrograms or 30 micrograms HA of H5N1 clade 1*
A/Vietnam/1194/04 split virion) either non-adjuvanted, or in
combination with GSK's novel proprietary adjuvant system, against
the drifted clade 2 A/Indonesia/5/05 strain. Two doses were
administered 21 days apart and blood samples collected on Days 0,
21 and 42. The conventional 4- fold increase in neutralizing
titers, before and after vaccination, was used to assess
seroconversion.

* A clade is the name given to groups of viral variants that are
closely related from an evolutionary standpoint

Second Study

Protection against challenge with a variant H5N1 strain in an
animal model with a low dose adjuvanted split H5N1 vaccine

Four animal test groups (N=23) were immunized intramuscularly
with 15, 7.5, 3.8 or 1.7 micrograms of H5N1/A/Vietnam/1194/04
(clade 1; NIBRG-14) vaccine containing a novel proprietary adjuvant
system. The 2 control groups were immunized with either the
adjuvant alone or the non-adjuvanted H5N1/A/Vietnam/1194/04 vaccine
(15 micrograms). Animals were vaccinated on days 0 and 21 and
challenged on day 49 with 105 TCID50 (50% Tissue Culture Infective
Dose*) of H5N1/ A/ Indonesia/5/05 (clade 2).

* The quantity of a cytopathogenic agent, i.e. such as a virus,
that will produce degenerative changes (or a diseased condition) in
50% of the cell cultures inoculated.

About GlaxoSmithKline

GlaxoSmithKline is one of the world's leading research-based
pharmaceutical and health care companies, and is committed to
improving the quality of human life by enabling people to do more,
feel better and live longer. For company information visit:
www.gsk.com.

About GSK Biologicals

GSK Biologicals, based in Rixensart, Belgium, is the vaccine
division of GlaxoSmithKline. As one of the world's leading vaccine
manufacturers, GSK Biologicals employs more than 1,500 scientists
devoted to discovering new vaccines and developing more
cost-effective and convenient combination products to prevent
infections that cause serious medical problems.

Editor's Note
GSK's 2005-2007 Milestones in Pandemic Preparedness

-- 2005: GSK made three important acquisitions in North America:
a vaccine manufacturing site in Marietta for cell-culture-based flu
vaccines and secondary operations; Corixa Corporation, for its work
in developing innovative adjuvants designed to stimulate immunity;
and ID Biomedical, which

offered a significant increase in flu vaccine manufacturing
capacity to help address both seasonal and pandemic influenza
threats.

-- May 2006: GSK received an HHS contract worth $274 million to
develop cell-culture technology to speed the development of new
cell culture-based seasonal and pandemic influenza vaccines, and to
scale-up cell culture manufacturing capability at GSK's Marietta,
PA site.

-- July 2006: Clinical studies announced by GSK showed promising
preliminary results on the potential antigen-sparing properties of
its candidate pre-pandemic influenza vaccine.

-- September 2006: GSK reached an agreement with the Simcere
Pharmaceutical Group of Nanjing, China, granting the right to
manufacture and sell the anti-viral influenza treatment zanamivir
in China, Indonesia, Thailand, Vietnam and all Least Developed
Countries.

-- October 18, 2006: GSK signs contracts with Switzerland to
supply its split pre-pandemic antigen and proprietary adjuvant for
stockpiling, in addition to an Advanced Purchase Agreement (APA)
for its pandemic vaccine in the event a pandemic is declared.

-- November 2006: GSK received a $40 million initial order for
bulk H5N1 antigen from HHS.

-- December 15, 2006: GSK announces that Daronrix(TM) its
alum-adjuvanted whole virus candidate pandemic vaccine; received a
positive opinion from the Committee for Medicinal Products for
Human Use.

-- January 2007: GSK receives from the HHS a $63.3 million
contract to develop antigen-sparing H5N1 pandemic influenza
vaccines.

-- January 2007: GSK begins supplying its antiviral, Relenza(R)
(zanamivir for inhalation), to the U.S. government and begins
working with private-sector businesses and other organizations to
provide Relenza(R) as part of their business continuity
planning.

-- January 4, 2007: GSK entered into an APA with the Danish
government to supply its split candidate pandemic antigen and
proprietary adjuvant once a pandemic has been declared.

-- January 23, 2007: GSK announced that the file for their
proprietary adjuvanted split antigen pre-pandemic vaccine has been
accepted for review by the CHMP.